Gas-powered and controlled foghorn



Nov. 19, 1968 5.1.. WARREN ET 3,411,476

GAS-POWERED AND-CONTROLLED FOGHORN Filed Jan. 24, 1966 E3208 mm mm v R 0 192x950 Ill m m m 539m E0 mm L H v mm 8. 6 mm N w llllr 3 mm 8. mm N v w m P mm 1 ow mZmOI ATTORNEYS United States Patent 3,411,476 GAS-POWERED AND CONTROLLED FOGHORN Sammie L. Warren and Roscoe H. Boyd, Jr., Cameron, La., assignors to Warren & Boyd Service Company, Inc., Cameron, La., a corporation of Louisiana Filed Jan. 24, 1966, Ser. No. 522,442

12 Claims. (Cl. 116-70) The present invention relates to fog warning devices and, particularly to gas powered fog-horns which are fail-safe.

With the'development of off-shore oil drilling, the presence of great numbers of off-shore drilling rigs has created a considerable hazard to boats navigating those waters. Not only are hazards created by the mere physical presence of the drilling rigs themselves, but to a large extent they are due to the increased water trafiic caused by the normal operation of the rigs. That is, a great increase in trafiic results from the necessity of providing transportation for the crews who work on the rigs and for the parts and supplies necessary to maintain their operation. These boats, then, that transport the men and supplies are thus added to the already present traflic of fishing boats and other such craft as are customarily found in such coastal waters, as for example, the Gulf of Mexico, an area which presently contains a relatively large number of off-shore drilling rigs and constructions. Thus, there is the necessity for providing navigational warning devices on these constructions, which devices must comply with stringent Coast Guard requirements designed to prevent, or at least minimize collisions therewith. This is especially so with respect to fog warning devices and fog horns, in particular.

Heretofore, it has been common practice on such olfshore constructions to utilize fog-horns for providing the standard two second blast and eighteen second period of silence, where the power for such horns is supplied by a pair of diesel engines and compressors arranged such that one engine and compressor normally drives the horn, and in case of failure, for any reason, the other engine and compressor are automatically connected to the horn in order to supply the required power. In this manner a fail-safe system has been provided.

However, it has been generally found that installation and maintenance costs of such a system are extremely high. In addition, the necessities which are incident to such a system, such as the continuous supplying of appropriate fuel therefor, places an even greater burden on the water trafiic the vicinity thereabout. Thus, the twin diesel and compressor systems heretofore available and presently used represent, at best, an uneconomical method of pro- 'viding' the power and timing means for driving off-shore fog-horns in a fail-safe manner.

Accordingly, it is an object of the present invention to provide a fail-safe fog-horn system which does not require auxiliary power equipment and which can be directly powered by the supply of natural gas which is generally found at the site of such off-shore drilling rigs. The pres-,

ent invention utilizes a gas storage tank which is fed by two gas supply lines, a primary and secondary supply, respectively. The gas output lines from the storage tank provide a gas flow which is capable of driving a gas control system which includes a primary and secondary timer. The gas control system provides two general functions. First, it provides the standard two second blast and eighteen second period of silence; and secondly, it provides a means for switching, or changeover, from the primary timer to the secondary timer in such case where thehorn fails to blow for a period longer than one minute. In this manner the present invention provides a fail-safe fog-horn system which is in compliance with the Coast Guard regulations therefor. The system requires only the source of natural gas, which is generally available at such off-shore drilling rigs, as previously mentioned, and eliminates the need for any diesel power equipment or internal combustion engines which would require the transportation of fuel to such construction sites. The system of the present invention utilizes generally pneumatic components which are commercially available and the cost of the system is only approximately one-fifth of the cost of the twin diesel and compressor system commonly used for such purposes. Furthermore, the system of the present invention provides even greater reliability as compared with the reliability of a system which is supplied by diesel power.

In addition to the provision of primary and secondary timers, the secondary timer acting as a back-stop for the primary timer, the system also provides a primary gas supply as well as a secondary gas supply, which adds an additional safety factor. Therefore, should the primary gas supply system freeze, which might be the most common cause of trouble in the supply, the secondary gas supply would automatically take over. The secondary supply contains means for removing the water vapor in the gas through the use of a dry desiccant dehydrator, which obviates the possibility of the secondary supply freezing. When the primary supply thaws out, it then returns to operation. The secondary supply will then cease and the system will draw only on the primary supply in a manner to be described hereafter.

The gas control system, in accordance with the present invention, comprises three snap-action pilots which are pressure differential responsive and which control threeway microvalves. The primary timer comprises a first snap-action pilot and valve unit which is so connected and arranged such as to provide timing and cycle control for the horn. The secondary timer is similar to the primary timer and is connected to provide the same timing and cycle functions as the primary timer. The secondary timer, ordinarily, during normal operation remains inactive, serving only as a back-stop unit to the primary timer. The third snap-action pilot and valve unit together with pressure integrating means serve the function of maintaining the primary timer operating during normal horn operation. However, when the horn fails to operate for a predetermined period of time, e.g., a period of one minute, the third snap-action pilot and valve unit automatically switches the gas powered horn system to the secondary timer.

It is thus another object of the present invention to provide a gas powered fog-horn having greater reliability of operation than any system heretofore known.

It is still another object of the present invention to provide a fog-horn system which is more economical, both in initial cost and in maintenance cost, than any system heretofore known.

It is a further object of the present invention to provide a gas powered fog-horn which comprises a dual gas supply line and primary and secondary pneumatic timer systems to achieve an extremely high degree of reliability in the operation of the horn.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawing, wherein:

FIGURE 1 is a schematic diagram of the system in accordance with the present invention, and

FIGURE 2 is a diagrammatic illustration of the construction of a snap-action pilot and valve unit utilized in the present invention.

Referring now to FIGURE 1 there is illustrated, in schematic form, the entire system in accordance with the present invention. The system can be divided into three general subsystems; namely, the gas supply system 200, the horn feed system 300 and the gas control and timing system 400. The gas supply system 200 comprises generally two gas supply pipes 34 and 37, a dryer and a volume and liquid fallout storage tank 39. The primary source of gas is supplied by a primary supply pipe 37 through a A-inch needle valve 38 to a At-inch pressure regulating valve 36. The output of valve 36 is connected to the volume and liquid fallout storage tank 39. A secondary supply of gas is provided by the secondary supply pipe 34 which is connected to the dryer 35 through a A-inch needle valve 33. The output of the dryer 35 is also coupled to the volume and liquid fallout storage tank 39 through a At-inch pressure regulating valve 32. A 150-lb. gauge 31 is connected to the system between the pressure regulator 32 and the tank 39 in order to monitor the pressure at this point.

Two output pipes 55 and 56 connect the gas supply system to the horn feed system by each supplying gas from tank 39 as shown in FIGURE 2 through two A- inch, 150 lb. needle valves 28 and 29. The output of each needle valve is coupled to connections 71 and 72, respectively, each of which provides a branch to couple the storage tank outputs to A-inch quick open diaphragm valves 24 and 27, and also to pipes 58 and 59 which are both coupled to pipe 57. Pipe 57 joins the horn feed system 300 to the gas control system 400 and branches at junction 74, diverting the gas flow to pipes 60 and 61.

Pipe 61 is connected to dryer 19, which in turn, is connected to a filter .18 (for example, of the cellulose type) through pipe 62. The output of filter 18 is connected to pressure regulator 20 (Fisher Governor Company type Series 67 Regulator such as described in Fisher Catalog No. 96-7691 which is connected to the common port 44 of microwave 81, associated with the changeover snapaction pilot and valve unit 92. A fifty pound pressure gauge 17 is provided between the pressure regulator 20 and the aforesaid common port 44. Pipe 95 connects the port 47 of microvalve 81 to the normally open port of the microvalve 84, associated with the secondary timer 91. Pipe 96 connects the port 46 of microvalve 81 to the normally open port of microvalve 82, associated with the primary timer 90. The common port 49 of the microvalve 82 is connected to an adjustable orifice valve 16, (such as the Manatrol check, needle and flow control valve illustrated in the Womack Machine Supply Company Designers Manual and Catalog 365E at page 61), the output of which, is connected to the upper diaphragm chamber of the snap-action pilot 12 (for example, of the type illustrated as Model No. 664-CDM-2501-B2 in the March 1963 National Tank Company catalog). The normally closed port 48 is terminated with an adjustable orifice valve 15 (of the same general type as valve 16). Similarly, the common port 43 of microvalve 84 is connected to an adjustable orifice valve 14 (of the same general type as valve 16), the output of which, feeds the upper diaphragm chamber of the snap-action pilot 10 (of the same general type as pilot 12). The normally closed port 42 is terminated with an adjustable orifice valve 13 (of the same general type as 'valve 16).

Microvalve 85, associated with the secondary timer 10, utilizes only two ports 51 and 52, while microvalve 83, associated with the primary timer 90, also utilizes only two ports 53 and 54.

Referring now to microvalve 83, the common port 54 is connected to a quick-open diaphragm valve 27 (for example National Tank Company Model No. 657-DSG- 7501) via pipe 97, while the common port of microvalve 85 is connected to the quick-open diaphragm valve 24 (of the same general type as valve 27) via pipe 98. Both the normally closed ports 51 and 53 are joined to pipe 76 at junction 75 which is connected to junction 74 through a A-inch pressure regulator valve 23 (of the same general type as regulator valve 20). The junction 75 has also provided thereat, a fifty-pound pressure gauge 22, for measuring the pressure at that point. The upper diaphragm chamber 7 of the changeover snap-action pilot 11 is connected to junction 5 at the mouth of the volume bottle 99. Also coupled thereto is an adjustable orifice valve 21 (of the same general type as orifice valve 16), the output of which is connected to junction 8 via a /2- inch pipe 9. Junction 8 is interposed in the %-inch pipe 40, which directly feeds the horns 41. Pipe 40 terminates, .on the opposite end, at junction 6 which couples two At-inch check valves, 25 and 26, thereto. The input ports of valves 25 and 26 are connected to the output ports of the quick-open diaphragm valves 24 and 27, respectively.

In the operation of the system, both the primary supply pipe 37 and the secondary supply pipe 34 feed gas to the volume and liquid fallout storage tank 39 until the pressure inside the tank reaches 60 pounds. At this time the secondary supply cuts off and the primary supply continues providing gas until the pressure reaches 70 pounds. The primary supply pressure regulator 36 is set to feed or hold a continuous pressure of 70 pounds on the storage tank 39. The secondary regulator 32 is set to hold 60 pounds. Since the primary supply regulator pressure is maintained at a higher value than the secondary supply pressure, as long as the primary regulator holds 70 pounds, the secondary does not provide any gas to the storage tank 39. However, should the primary regulator freeze off or not operate, causing the pressure to drop below 60 pounds, the secondary regulator would maintain a pressure of 60 pounds on the volume tank, which pressure is sufficient for satisfactory system operation. Thus, the utilization of a primary and secondary supply to provide the gas necessary for the operation of the system assures a greater probability of reliable operation.

The greatest cause of potential trouble in the gas supply system, as previously mentioned, is the freezing of the lines of supply. If the primary gas supply freezes and the secondary gas supply begins to operate, there is little possibility that the secondary gas supply will also freeze, since within the secondary supply line is located the dry desiccant dehydrator 35. When the primary system thaws, it then returns to operation and the dry desiccant dehydrator in the secondary supply line may then be changed or renewed. A dehydrator or dryer, might also be placed in the primary supply, however, this would tend to increase the maintenance required since it would then be necessary to change or renew two desiccants instead of one.

Carried with the gas, which is supplied by the primary and secondary supply pipes, will be a certain amount of liquid which will settle in the storage tank 39 and be forced back into the pipe line through a blow case connection from the volume tank drain, as will be explained in greater detail hereinafter. Both pipes 55 and 56 carry the gas under pressure from the storage tank 39 through needle valves 28 and 29 to the input ports of valves 24 and 27. However, since the quick-open diaphragm valves 24 and 27 are normally in a closed position, the gas flows through pipes 58 and 59 to junction 73 and then through pipe 57 to junction 74. There, the gas is diverted to pipes 60 and 61. The gas flowing through pipe 61 is dehydrated, or dried, in dryer 19 and passed through filter 18 via pipe 62 in order to assure trouble free operation of the snap-action pilots 10, 11 and '12 and the equip: ment associated therewith. The elimination of foreign particles and water from the gas flow reduces corrosion and failure of the parts due to the presence of such matter, if any, in the system.

The gas is then fed to the common port of microvalve 81, associated with the changeover snap-action pilot 11, the operation of which is more clearly described with reference to FIGURE 2. FIGURE 2 illustrates diagrammatically the general construction of the snap-action pilots 10 and 12. The construction of the snap-action pilot 11 is similar to 10 and 12, but is modified in some respects. Namely, as shown in FIGURE 1, there is only one microvalve assembly instead of the two associated with the snap-action pilots and 12, and in addition thereto, there are some internal modifications which will be described hereafter.

The three-way microvalves are represented by 109 and 110. Each has three ports 101, 102 and 103 associated with the microvalve 110 and 104, 105 and 106 associated with the microvalve 109. The microvalves 110 and 109 each have a common port 101 and 105, respectively, which may be switched to provide a continuous flow to either port 102 or 103 on the one hand, and port 104 or 106 on the other. The switching action of each microvalve is controlled by levers 115 and 114 and the operation of such levers is provided by a reciprocable shaft 111, having spaced apart collars 112 and 113 fixed at one end thereof. The opposite end of shaft 111 is fixed to a movable diaphragm 108 disposed in the diaphragm chamber 100 and is maintained in a normally upward position by spring 109. Port 107 is the gas input port to the upper diaphragm chamber, while disposed in port 116 is a bleeder filter which slowly relieves the pressure in the lower diaphragm chamber 117 and permits pressure equalization thereof. In the normal position of the snap-action pilot, where spring 109 maintains diaphragm 108 biased in its upward position, as illustrated in FIG- URE 2, ports 103 and 106 are in their normally open position, that is, in this position common ports 101 and 105 are each connected respectively to ports 103 and 106 to provide continuous flow therethrough. Ports 102 and 104 are closed. When the gas pressure that is supplied through port 107 into the upper diaphragm chamber is sufiiciently great such as to overcome the bias force of spring 109, the diaphragm 108 snaps into a downward position causing shaft 111 to move vertically downward and collar 112 to engage levers 114 and 115. This action snaps each lever to its most downward position resulting in the closing of the normally open ports 103 and 106 and the opening of the normally closed ports 102 and 104 such that in this condition the common ports 101 and 105 are connected to ports 102 and 104, respectively. When the pressure is relieved in the upper diaphragm chamber 100, the spring 109 snaps the diaphragm 108 into its upward position moving shaft 111 in an upward vertical direction which causes collar 113 to engage levers 114 and 115 moving them into their most upward position. This action results in the snap-action pilot and valve unit returning to its original condition.

The modifications previously referred to that are required for the snap-action pilot utilized as the changeover pilot 11 are three fold. First, only one three-way microvalve 110 is required. Second, the microvalve ports are arranged such that port 103, corresponding to port 46 in FIGURE 1, is normally closed when the diaphragm is in its upward position, while port 102, corresponding to port 47, is normally open. Third, the collar 112 is omitted, leaving only collar 113 on shaft 111 for reasons which will become clear hereinafter. In addition means are provided to permit manual actuation of the microvalve lever, such means being, for example, merely an opening in the housing.

Referring again to FIGURE 1, with respect to the operation of the system, the gas following the path 61, 62 passes through the common port 44 of the changeover snap-action pilot 11 to the normally closed port 46. Thus, initially, the snap-action pilot and microvalve lever may be depressed manually, opening the port 46 to the common port 44, which permits the gas to flow through the pipe 96 to the normally open port 50 of microvalve 82. Alternatively, the snap-action pilot diaphragm may be depressed initially by the gas operation of the horn through the secondary timer 91, since port 47 of microvalve 81 and port 45 of microvalve 84 are both normally open. The gas providing the horn blasts, so initiated, flows through pipe 9 and depresses the pilot 11 diaphragm.

Then, the microvalve lever may be manually depressed. (The manual depression of the lever is necessary of course, since the collar corresponding to 112 in FIGURE 2 is not present.) This also, will permit the gas to flow from the common port 44 to the normally open port of microvalve 82 in the manner aforementioned. The gas then flows to port 49 and through the orifice valve 16 to the upper diaphragm chamber of the primary timer 12. The orifice valve 16 is adjusted to bleed off the gas flowing therethrough such that it requires a period of 18 seconds to provide sufiicient gas pressure in the upper diaphragm chamber to cause the diaphragm to snap into its lower position. This action, as previously described, causes the normally closed port 48 and the normally closed port 53 to be opened to the common ports 49 and '54, respectively, closing port 50.

Thus, during this period of time two actions occur. First, the gas flow from pipe 57, at junction 74, flows through pipe to port 53, to the common port 54 of microvalve 83, and through pipe 97 to the quick-open diaphragm valve 27. This pressure is suflicient to open valve 27, permitting the gas from the volume storage tank 39 to pass through pipe 56 and check valve 26 to junction 6 and up pipe 40 and to the horns 41. Second, when the common port 49 of the microvalve 82 is connected to the port 48, the gas pressure which has accumulated in the upper diaphragm chamber is permitted relief through the adjustable orifice valve 16 and the valve 15, such valves combined, being adjusted for sufficient gas discharge bleed in the required time of two seconds. At this time, since the pressure in the upper diaphragm chamber is no longer sufficient to retain the diaphragm in its lower position, the spring contained therein, forces the diaphragm to its normal position, lifting the control shaft and closing valve ports 48 and 53. The closing of port 53 cuts off the horn blast. Thus, the cycle is repeated with gas flowing through the normally open port 50, to port 49, through the orifice valve 16, and into the upper diaphragm chamber for a period of eighteen seconds, at which time the pressure in the upper diaphragm chamber has attained a predetermined value sufficient to snap the diaphragm into its lower position. The normally open port 50 is closed, ports 48 and 53 are opened, permitting another two second blast on the horn, the gas being discharged from the upper chamber through orifice valves 15 and 16.

During these repetitive twenty-second cycles, i.e., two seconds of blast and eighteen seconds of silence, the diaphragm of the snap-action pilt 11 must be maintained in its downward position, permitting gas to flow from j-unction 44 to the normally closed port 46. During the two second blasts from the horns 41, gas flows from junction 8 through inch pipe 9 to the orifice valve 21, and then to the upper diaphragm chamber 7. During this process the volume bottle 99 will fill to a certain given pressure as the gas passes andv divides at junction 5. Thus, during the eighteen second period of the cycle when no gas flows through pipe 40, the pressure developed in volume bottle 99 will cause the upper diaphragm chamber to retain a pressure therein greater than the minimum required to maintain the diaphragm in its downward position for a period of one minute, after which the diaphragm will snap to its normally upward position. The one minue time period is set by adjustment of the orifice valve 21, and the orifice valve and volume bottle integrate the gas pressure to the chamber 7. Should the horn fail to blow for a period longer than one minute, the continuous bleeding of valve 21 causes the pressure on the diaphragm of pilot 11 to decrease below that which results in the diaphragm snapping to its normally upward position. This, in turn, causes the shaft corresponding to 111 in FIGURE 2 to move upward, following the motion of the diaphragm. As shaft 111 moves to its uppermost position, the collar corresponding to 113 engages the microwave switch lever causing the common port 44 to switch from the port 46 to the normally open port 47.

Thus, in this manner, the gas supply then flows through pipe 95, through the normally open port 45 in microvalve 84, to the common port 43 and through the adjustable orifice valve 14 to the upper diaphragm chamber of the pilot 10. The operation of the secondary timer 91 is similar to the operation of the timer 90 such that for a period of eighteen seconds, until the pressure is sufiicient in the upper diaphragm chamber of pilot 10 to cause the diaphragm to snap into its downward position, the port 45 is open and ports 42 and 51 are closed. After the eighteen second interval, set "by adjustment of orifice valve 14, the port 45 is closed and the port 42 is opened to the common port 43, allowing the gas pressure in the diaphragm chamber to be relieved through both orifice valves 14 and 13, which relief takes place in two seconds. During this period of two seconds the common port 52 of the microvalve 85 is connected to provide a flow path to the normally closed port 51. Further, during this required two second interval, the gas flowing from pipe 76 through ports 51 and 52, and through pipe 98 to the quick-open diaphragm valve 24 causes the valve 24 to open. This action permits the gas flow from pipe 55 to pass through unidirectional check-valve 25 to pipe 40 and causes a two second blast of horns 41. The gas flow is blocked from interfering with the operation of the valve 27 by the presence of check-valve 26. During this period of operation, the gas flow from junction 8, pipe 9, and through orifice valve 21, over volume bottle 99 and to the upper diaphragm changeover pilot 11 continues as with the operation of the primary timer 90. Since the construction of pilot 11 is modified as compared with the construction of pilots 10 and 12, by the omission of collar 112 as shown in FIGURE 2, when the pressure in the upper diaphragm chamber 7 of snapper 11 reaches, again, a sufiicient value to cause the diaphragm to snap to its lower position, the microvalve 81 remains unchanged since with the omission of collar 112 there is no mechanism for engaging and depressing the lever of the microvalve. Thus, the timer 91 will continue to operate indefinitely until the system is reset externally by actuating the lever of microvalve 81 to its downward position. This may be accomplished by merely actuating the lever by hand through an opening in the housing provided therefor, or alternatively, may be accomplished by remote means such as an electric solenoid or a hydraulic or pneumatic piston arrangement. This, of course, causes the port 47 to close and the port 46 to open, bringing the system, once again, to its initial operating condition utilizing the primary timer 90. As is now apparent, the omission of collar 112 in the pilot 11 is necessary in order to prevent the system from oscillating between the primary and secondary timers when a fault occurs in the former. It is understood, of course, that other means might be utilized to prevent such system oscillation as will be apparent to workers in the art.

During the operation of the system and the primary and secondary supply, a certain amount of liquid is mixed with the gas and carried within the storage tank 39. Such liquid settles, or falls out, to the bottom of the tank and is put back into the pipeline through a blowcase connection (not shown) from the volume tank drain located near the bottom of the tank. Thus, the blowcase accumulates the liquid at a pressure of about 70 pounds and when it is full, all valves are closed, and the pressure is increased to equal the line pressure. The liquids are then gravitated back into the line in a manner known in the art.

A system has thus been disclosed and described for operating a gas powered fog-horn which is fail-safe and economical and which comprises novel features providing an extremely high degree of reliability.

While we have described and illustrated one specific embodiment of our invention, it will be clear that variation of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

We claim:

1. An acoustical signal device comprising a source of gas under pressure; a gas actuated acoustic transducer; a pair of gas fiow paths each interconnecting said source and said transducer; primary and secondary selectively actuable timer means, each for cyclically passing and blocking flow of pressurized gas between said source and said transducer by a respective one of said pair of gas flow paths; switching means having at least first and second operative states, for rendering said primary timer means actuated and said secondary timer means unactuated in said first operative state and for rendering said primary timer means unactuated and said secondary timer means actuated in said second operative state; and control means responsive to failure of said transducer to be actuated for a predetermined period of time for actuating said switching means to said second operative state.

2. The signal device according to claim 1 wherein said actuable switching means includes a pressure differential responsive means and a switchable valve means, and wherein said control means comprises a pressure integrating means; and wherein is further provided means for connecting said switchable valve means such that it selectively interconnects said source with said primary and said secondary timer means in response to actuation by said pressurized differential responsive means; means for connecting said pressure differential responsive means to be actuated by the output of said pressure integrating means; means for connecting said pressure integrating means to said gas flow paths whereby said pressure differential responsive means maintains said switchable valve means in one selected position corresponding to said first operative state of said actuable switching means during the presence of a given pressure in either of said gas flow paths and actuates said switchable valve means to another position corresponding to said second operative state of said actuable switching means in the absence of a given pressure in either of said gas flow paths during said predetermined period of time.

3. The signal device according to claim 1 wherein said source of gas under pressure comprises a storage means and a first and second supply means coupled thereto.

4. The signal device according to claim 3 wherein one of said supply means includes means for dehydrating the gas flowing therethrough.

5. The signal device according to claim 3 wherein said first supply means normally feeds said gas under pressure to said storage means; said source further comprising means for preventing said second supply means from feeding said storage means whenever the pressure in said storage means is greater than a given value and permitting said second supply means to feed said storage means whenever said pressure is lower than said given value.

6. The signal device of claim 2 wherein said pressure integrating means includes an orifice valve having an input port and an output port in series with both said gas flow paths and a volume bottle coupled to said output port.

7. A system for providing a cyclical alarm signal comprising:

a source of pressurized gas;

transducer means having a gas inlet port and responsive to application of pressurized gas to said gas inlet port for generating an alarm signal;

first and second gas flow paths, each for conducting pressurized gas from said source to said gas inlet port;

first switching means disposed in said first flow path and having two discrete states wherein upon application of a first control signal to said first switching means the latter assumes a first state in which it permits flow of pressurized gas from said source to said gas inlet port via said first flow path and wherein in the absence of said first control signal at said first switching means the latter assumes a second state in which it blocks flow of pressurized gas from said source to said gas inlet port via said first flow path; a second switching means disposed in said second flow path and having two discrete states wherein upon application of a second control signal to said second switching means the latter assumes a first state in which it permits flow of pressurized gas from said source to said gas inlet port via said second flow path and wherein in the absence of said second control signal at said second switching means the latter assumes a second state in which it blocks flow of pressurized gas from said source to said gas inlet port via said second flow path; first selectively actuable timer means for cyclically applying said first control signal to said first switching means at a specified frequency whenever said first timer means is actuated; second selectively actuable timer means for cyclically applying said second control signal to said second switching means at said specified frequency whenever said second timer means is actuated; timer selector means having a first operational mode for maintaining said first timer means actuated and said second timer means unact-uated and having a second operational mode for maintaining said second timer means actuated and said first timer means unactuated, said timer selector means including: pre-set means for placing said timer selector means in said first operational mode at the start of a system operational sequence, sensing means for sensing the frequency of application of pressurized gas to said gas inlet port, and controller means responsive to a predetermined decrease of the frequency of the application of said pressurized gas to said gas inlet port for placing said timer selector means in said second operational mode. 8. The system according to claim 7 wherein said source of pressurized gas includes:

a gas storage tank; a first gas supply pipe for supplying pressurized gas to said storage tank; a second gas supply pipe for supplying pressurized gas to said storage tank; first pressure regulator means for cutting off the supply of pressurized gas to said storage tank from said first supply pipe whenever the gas pressure in said storage tank exceeds a first predetermined pressure; second pressure regulator means for cutting off the supply of pressurized gas to said storage tank from said second supply pipe whenever the pressure in said storage tank exceeds a second predetermined pressure, wherein said second predetermined pressure is less than said first predetermined pressure; and output port means for supplying pressurized gas from said tank to said first and second flow paths. 9. The system according to claim 8 further comprising means for dehydrating the gas flowing into said storage tank from said second supply pipe.

10. The system according to claim 8 wherein said output port means comprises first and second individual output ports formed in said storage tank and connected to respective ones of said first and second flow paths.

11. The system according to claim 7 wherein said sensing means in said timer selector means comprises integrator means for providing a gas pressure signal as a function of the frequency of application of pressurized gas to said gas inlet port at said transducer;

wherein said controller means comprises: a pressure responsive actuator responsive to said gas pressure signal for maintaining a first position corresponding to said first operational mode when said gas pressure signal remains above a predetermined pressure and for maintaining a second position corresponding to said second operational'mode when said gas pressure signal falls below saidpredetermined pressure, said predetermined pressure corresponding to that which is provided by said integrator means when the frequency of application of gas pressure to said gas inlet port experiences said predetermined decrease; and valve means actuable by said pressure-responsive actuator for applying a gas pressure actuating signal to said first timer means when said pressureresponsive actuator is in its first position and for applying said gas pressure actuating signal to said second timer means when said pressure-responsive actuator is in its second position.

12. The system according to claim 11 wherein said first and second timer means each comprise:

an inlet port for receiving said gas pressure actuating signal from said timer selector means;

a pressure responsive member having a first position assumed in response to application of said gas pressure actuating signal thereto and a second position assumed in the absence of application of said gas pressure actuating signal thereto;

a flow path between said inlet and said pressureresponsive member for said gas pressure actuating signal, said flow path including delay means for providing a first predetermined time delay between the time of application of said gas pressure actuating signal to said inlet port and to said pressure-responsive member;

valve means actuable by said pressure-responsive member and having a first condition corresponding .to the first position of said pressure-responsive member in which pressure applied to said pressure-responsive member is exhausted to ambient pressure through further delay means.

References Cited UNITED STATES PATENTS LOUIS J. CAPOZI, Primary Examiner. 

1. AN ACOUSTICAL SIGNAL DEVICE COMPRISING A SOURCE OF GAS UNDER PRESSURE; A GAS ACTUATED ACOUSTIC TRANSDUCER; A PAIR OF GAS GLOW PATHS EACH INTERCONNECTING SAID SOURCE AND SAID TRANSDUCER; PRIMARY AND SECONDARY SELECTIVELY ACTUABLE TIMER MEANS, EACH FOR CYCLICALLY PASSING AND BLOCKING FLOW OF PRESSURIZED GAS BETWEEN SAID SOURCE AND SAID TRANSDUCER BY A RESPECTIVE ONE OF SAID PAIR OF GAS FLOW PATHS; SWITCHING MEANS HAVING AT LEAST FIRST AND SECOND OPERATIVE STATES, FOR RENDERING SAID PRIMARY TIMER MEANS ACTUATED AND SAID SECONDARY TIMER MEANS UNACTUATED IN SAID FIRST OPERATIVE STATE AND FOR RENDERING SAID PRIMARY TIMER MEANS UNACTUATED AND SAID SECONDARY TIMER MEANS ACTUATED IN SAID SECOND OPERATIVE STATE; AND CONTROL MEANS RESPONSIVE TO FAILURE OF SAID TRANSDUCER TO BE ACTUATED FOR A PREDETERMINED PERIOD OF TIME FOR ACTUATING SAID SWITCHING MEANS TO SAID SECOND OPERATIVE STATE. 